Author:

Johan Frenje(MIT-PSFC)

Over the last few decades, ion stopping in weakly- to strongly-coupled
High-Energy-Density (HED) plasmas has been subject to extensive analytical
and numerical studies, but only a limited set of experimental data exists to
check the validity of these theories. Most of these experiments also did not
probe the detailed characteristics of the Bragg peak (peak ion stopping)
where the ion velocity is similar to the average thermal electron velocity.
To the best of our knowledge, only one exploratory attempt to do this was
conducted by Hicks et al.,\footnote{D. G. Hicks et al., Phys. Plasmas 7, 5106 (2000).} who were able to describe
qualitatively the behavior of the Bragg peak for one plasma condition. The
work described in this presentation makes significant advances over previous
experimental efforts by quantitatively assessing the characteristics of the
ion stopping, ranging from low-velocity stopping, through the Bragg peak, to
high-velocity stopping for different HED plasma conditions. This was
achieved by measuring the energy loss of DD-tritons,
D$^{\mathrm{3}}$He-alphas, DD-protons and D$^{\mathrm{3}}$He-protons, with
distinctly different velocities, and the results indicate that the stopping
power varies strongly with T$_{\mathrm{e}}$ and n$_{\mathrm{e}}$. This
effort represents the first experimental test of state-of-art
plasma-stopping-power theories around the Bragg peak, which is an important
first step in our efforts of getting a fundamental understanding of DT-alpha
stopping in HED plasmas, a prerequisite for understanding ignition margins
in various implosion designs with varying hot spot areal density at the
National Ignition Facility.

*The work described here was performed in part at the LLE National Laser User's Facility (NLUF), and was supported in part by US DOE (Grant No. DE-FG03- 03SF22691), LLNL (subcontract Grant No. B504974) and LLE (subcontract Grant No. 412160-001G).

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2015.DPP.JI3.4